TABLESAMPLE SYSTEM_ROWS reads CONTIGUOUS rows from each sampled page, so
sequentially-imported near-duplicates (multi-image posts, variant sets) came
back adjacent and clustered in the showcase ("three near-identical in a row").
Sample limit*5 rows (spanning more pages) then ORDER BY random() before taking
limit — breaks the physical adjacency for much better spread, still cheap
(random() over a few hundred rows, not the whole table).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen
89dfa42e18